Conventionally, various tests and treatments are performed based on electrical signals transmitted by electronic components, such as a heat element, a pressure sensor, a temperature measurement thermistor and the like, set in an anterior end or an intermediate part of a tube of a catheter inserted into a body of a patient. Such an electronic component-loaded catheter is described, for example, in JP-A-11-56794 and JP-A-2001-170013.
The aforementioned “anterior end of a tube” means an end of a head of a catheter (tube) in a length direction, which is to be inserted into the body of a patient, and the “anterior end of a tube” in the following description in the present specification means an end of the head of a catheter (tube) in the length direction when inserted into the body of a patient, and the “posterior end of a tube” means another end of the tube, which is an opposite side from the head, in the length direction.
In the above-mentioned catheter comprising an electronic component in a tube, an electrical signal sent by an electronic component in the anterior end or an intermediate part of a tube inserted in the body of a patient is processed by a measuring apparatus connected to the posterior end of the tube outside the body of the patient. When operation of the aforementioned electronic component is to be controlled, it is remotely controlled by a control device connected to the posterior end of a tube outside the body of the patient. Therefore, a signal line to transmit an electrical signal between the electronic component and a measuring apparatus, a control device and the like needs to be installed in a tube of an electronic component-loaded catheter. As such signal line, signal cables such as a flat cable and the like have been conventionally used, as in the catheters described in the aforementioned JP-A-11-56794 and JP-A-2001-170013. Recently, however, for higher functions of electronic components to be set in a tube, this kind of catheter is required to contain an increased number of signal lines. When a number of signal cables is increased to contain many signal lines, a tube containing the signal cables needs to be made thicker. As a result, problems of lower operability of a catheter in a body of a patient, increased pain felt by the patient during operation of the catheter and possible damage in the body of the patient occur. Since a mounting site of an electronic component is limited to a specific area at a tip of a signal cable, a number of electronic components to be mounted is limited. In addition, since a position of electronic components to be mounted is limited to the tip of a signal cable, a place where the electronic components operate as well as their functions are problematically limited.
Therefore, the present inventors have considered using a flexible printed circuit board as a signal line to be installed in a tube. To be specific, since a flexible printed circuit board can form an ultrafine high density wiring, when it is used as a signal line to be installed in a tube, a number of signal lines can be increased without greatly increasing a thickness of the tube. Since a terminal mounting an electronic component can be formed at a given position in a flexible printed circuit board, moreover, positions and a number of electronic components to be installed can be easily designed.
When a flexible printed circuit board is inserted in a tube for use as a signal line, however, since the flexible printed circuit board needs to be formed in a long, linear pattern, a production cost of a product showing highly uniform properties becomes high. To be precise, in most cases, a photolithography step is included in production of a flexible printed circuit board, which uses a general-purpose exposing apparatus having an exposure area of generally about a 250 mm×250 mm square. When one linear flexible printed circuit board having a total length of not less than 300 mm is to be produced, it needs to be exposed to light multiple times in multiple steps, or an exposure mask having a considerably extended length needs to be prepared, or an exposure surface needs to have a considerably large linear length, which causes a high cost. Moreover, exposure at multiple times in multiple steps may result in occurrence of disconnection between exposed areas.
In addition, while a flexible printed circuit board is advantageous for decreasing a diameter of a catheter as compared to wire cables, a degree of freedom of movement in a tube is generally smaller than wire cables, and operability (deformability) of a catheter using a flexible printed circuit board as a signal line is not entirely satisfactory.
In view of the above-mentioned situation, a problem to be solved by the present invention is provision of a flexible printed circuit board for a catheter, which is sufficiently elongate for use as a signal line of a catheter, can be produced using a general-purpose production apparatus, and can improve a degree of freedom of movement in a tube, a catheter comprising the flexible printed circuit board and a production method thereof.